Comparing to general light sources such as incandescent lamps, fluorescent lamps, and the like, since light emitting diode light source (LED light source) and organic light emitting diode light source (OLED light source) are light, mercury-free, ultraviolet radiation free, flexible and used as a planar light source, they are considered as the new light sources with highly-potential perspective.
The light emitting device may include a plurality of OLED light sources. In other words, a plurality of OLED light sources with different properties may be combined to constitute the light emitting device. As shown in Table 1 below, the properties are, for example: rigidity or flexibility, different capabilities, different dimensions or shapes. In consideration of the different properties, in the general technique, for the light emitting device that operates under a particular condition, it is required to use a particular driving module to provide drive current.
TABLE 1CharacteristicCapabilityDimension/ShapeDrive currentRigidity55 Lumen/W53 × 55mm240 mA & 60 mAFlexibility60 Lumen/W100 × 100mm2100 mA & 150 mA & 230 mA90 Lumen/W140 × 140mm2300 mA & 480 mA200 × 50mm2150~160 mA & 230~245 mA213 × 113mm2570 mA320 × 110mm2500 mA & 800 mA320 × 320mm21600 mA & 2500 mA406 × 50mm2300 mA & 510 mARound-shape 109mm2150 mA & 230 mA
Accordingly, in the general light emitting device, some technical problems exist as described below. First of all, when the light emitting device operates differently from one condition to another, it is required to switch to different driving modules accordingly; thus, the cost of driving module cannot be effectively reduced.
Secondly, in the light emitting device, generally different resistors are used to set the protection voltage level for OLED light sources of different dimensions. Therefore, if shorted status occurs, there will be difference in detection of short-circuit voltage of the OLED light sources of different dimensions. In that case, it is difficult to accurately detect which OLED light source is in the shorted status.
Thirdly, in the light emitting device, in the operation condition of constant current, the brightness attenuation curves of different OLED light sources are different from one another. Thus, when one of the OLED light sources is damaged and needs replacement, after the replacement, there is problem of non-uniformity in the brightness of the replaced OLED light source and the rest of original OLED light sources, and the overall light emitting uniformity of the light emitting device is decreased.